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Lab Tech Flashcards

1
Q

The following will cause drift errors in an analytical balance EXCEPT
A. Balance door is open.
B. Balance is not levelled
C. Air currents are present in the laboratory.
D. Temperature of the balance and the sample to be weighed is the same.

A

D

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2
Q

Objects cannot be weighed when hot or warm. But if you were to take a sample out and wait for it to cool it would pick up moisture so it should be placed in a/an/at
A. oven
B. desiccator
C. room temp
D. fume hood

A

B

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3
Q

It is the nominal volume of water (or mercury) contained, or delivered by an article of volumetric glassware, at its reference temperature.
A. accuracy
B. calibration
C. capacity
D. measurand

A

C

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4
Q

A student is tasked to measure 12 mL of a liquid as precisely as possible. Which measuring device should be selected for this task?
A. 25 mL beaker
B. 25 mL graduated cylinder
C. 25 mL conical flask
D. 25 mL volumetric flask

A

B

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5
Q

Which of the following is TRUE about TC pipets?
A. TC means “to carry”.
B. It commonly does not have a colored band.
C. It is used if the liquid left in the pipet is already accounted.
D. None of the above.

A

D

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6
Q

A student needs to transfer his precipitant from the beaker to the filter paper. Which of the following would be the best procedure in order to ensure a quantitative transfer of the precipitate?
A. Most of the supernatant liquid is decanted then bulk of precipitate is transferred to filter paper through a stirring rod, then the beaker is washed with large volumes of wash solution.
B. Most of the supernatant liquid decanted first, then bulk of the precipitate is transferred through a stirring rod. The beaker is washed several times with small volumes of wash solution.
C. Solution is shaken, then immediately filtered; beaker is washed with big volumes of wash solution.
D. None of the above.

A

A

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7
Q

To determine the density of a liquid, which of the follewing should be used?
A. graduated cylinder
B. volumetric flask
C. pycnometer
D. pipette

A

C

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8
Q

Which is TRUE for a 19/22 stopper?
A. radius =19 mm, height = 22 mm
B. radius = 22 mm, height = 19 mm
C. diameter = 19 mm, height = 22 mm
D. diameter = 22 mm, height = 19 mm

A

C

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9
Q

Which technique is recommended for determining the odor of an unknown liquid in the laboratory?
A. Hold a test tube of the liquid under the nose and inhale the vapor.
B. Transfer a few drops of the liquid to the bench top and inhale the vapor from there.
C. Use a dropper to collect a small quantity of the vapor and squirt this under the nose while inhaling.
D. Use a hand to fan some of the vapor from the test tube to the nose and inhale.

A

D

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10
Q

The size of the sample taken for analysis depends on the ________
A. concentration of analyte
B. equipment to be used
C. specific chemical tests
D. all of the above

A

D

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11
Q

Possible sources of contamination during sample preparation include
A. reagents
B. glassware from previous experiment
C. equipment from previous experiment
D. all of the above

A

D

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12
Q

Which of the following can cause errors during the sample preparation?
I. Loss of sample during weighing or dissolution.
Il. Contamination by impurities in reagents and in the environment.
Ill. Changes in mass due to varying humidity and temperature.
IV. Obtaining nonhomogeneous sample from the bulk.
A. I and II only
B. I, III, and IV
C. I, II, and III
D. I, II, IlI, and IV

A

D

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13
Q

Method of passing the sample through a metal or plastic mesh of a uniform cross-sectional area to separate particles into uniform sizes.
A. sieving
B. milling
C. pulverizing
D. macerating

A

A

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14
Q

Which of the following can remove a fairly large amount of water from a sample that contains thermally labile material?
A. hotplate
B. freeze dryer
C. convection oven
D. microwave equipment

A

B

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15
Q

Sample preparation technique used prior to instrumental analysis of metals.
A. sieving
B. clean-up
C. acid digestion
D. liquid-liquid extraction

A

C

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16
Q

Which of the following should NOT be used during dry ashing?
A. Zirconium
C. Porcelain
B. Platinum
D. Glass

A

D

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17
Q

In an experiment to determine the percentage of water in a solid hydrate by heating, what is the best indication that all the water has been removed?
A. The solid melts.
B. The solid changes color.
C. Water vapor no longer appears.
D. Successive weighings give the same mass.

A

D

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18
Q

Which of the following statement(s) is(are) TRUE?
I. Dry ashing is primarily for proximate composition and for some types of specific mineral analyses.
Il. Wet ashing is done as a preparation for the analysis of certain minerals.
IlI. Microwave systems are now available for both dry and wet ashing to speed the processes.
A. I only
B. II only
C. I and Il only
D. I, Il, and Ill

A

C?

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19
Q

In the decomposition and dissolution of solids during sample preparation, which of the following is expensive and often the last resort?
A. fusion technique
B. simple dissolution
C. acid treatment using oxidation
D. dissolution using ultrasound and solvent

A

A

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20
Q

All of the following are properties of an organic solvent for extraction EXCEPT
A. dissolve the desired substance
B. react with the desired substance
C. not react or be miscible with water
D. has a low boiling point so it can be easily removed at a later purification step

A

B

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21
Q

This is done during liquid-liquid extraction to release the pressure build-up inside the separatory funnel during shaking.
A. stirring
B. venting
C. drawing
D. salting out

A

B

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22
Q

Which of the following should NOT be done when an emulsion is formed during extraction?
A. stirring the emulsion gently using a stirring rod
B. adding sal crystals to the mixture and then string it gently
C. adding a salt solution to the mixture and then stirring it gently
D. shaking the separatory funnel containing the mixture very vigorously

A

D

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23
Q

In liquid-liquid extraction, it is often necessary to determine the aqueous and organic layers. To test the layers, a drop of water can be added to the top layer. If the drop of water dissolves in the top layer, then the top layer is
A. organic
B. aqueous
C. denser
D. nonaqueous

A

B

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24
Q

This is used to remove trace amounts of water in organic solutions. This can be added to the AIr‹ pooled organic layers before removal of the organic solvent.
A. drying agent
B. boiling stone
C. seed crystal
D. none of the above

A

A

25
Q

A 5-g organic solid is dissolved in 100 mL of distilled water. What is the best way to recover most of the organic solid?
A. Single extraction using 150 mL ether.
B. Single extraction using 150 mL acetic acid.
C. Multiple extraction using three 50-mL portions of ether.
D. Multiple extraction using three 50-mL portions of acetic acid.

A

C

26
Q

Which of the following is/are considered in purification using crystallization?
I. Polarity
II. Solubility
III. Vapor pressure
A. I only
B. II only
C. I and Il only
D. I, II, and III

A

D

27
Q

Which of the following funnels should be used to filter hot mother liquor during recrystallization?
A. Hirsch funnel
B. Büchner funnel
C. long stem funnel
D. short stem funnel

A

D

28
Q

In crystallization, crystal phases can be interconverted by varying
A. temperature
B. pressure
C. viscosity
D. size

A

A

29
Q

All of the following statements are TRUE, EXCEPT
A. Two different pure substances have similar melting points.
B. An impure sample of a substance has a wider melting point range.
C. Melting point serves as an index of purity of a solid crystalline substance.
D. Every pure solid crystalline substance has a characteristic and unique melting point.

A

A

30
Q

The height equivalent of a theoretical plate or HETP has all of the following characteristics EXCEPT
A. It is defined by the van Deemter equation.
B. Equilibrium is attained at each height equivalent.
C. The smaller the value is, the better the separation attainable.
D. This quantity times column length is equal to the number of theoretical plates in the column.

A

B & D

31
Q

In this chromatographic method, the sample may be gas or liquid injected into a gaseous mobile phase.
A. gas chromatography
C. thin layer chromatography
B. affinity chromatography
D. high pressure liquid chromatography

A

A

32
Q

The following are properties of an open tubular or capillary column
EXCEPT
A. Poor resolution can be obtained.
B. Only small samples can be applied.
C. It has a long column length with small inner diameter.
D. It has a large number of plates that permit rapid separations of closely

A

A

33
Q

An air sample is subjected to gas chromatography for the analysis of Freon-11 (CCIF). The detector that is most suitable for this analysis is
A. TCD
B. ECD
C. FID
D. TSD

A

B

34
Q

Analysis and separation of industrial products like soap and synthetic detergents is done using
A. Thin layer chromatography
B. Gas chromatography
C. Partition chromatography
D. lon exchange chromatograph

A

B

35
Q

An advantage of HPLC over GC for the separation and measurement of high molecular weight compounds is that
A. HPLC columns and detectors are simpler and less expensive.
B. The preparation of volatile derivatives is not necessary in HPLC.
C. HPLC systems are always operated under constant conditions of eluant temp and composition.
D. The sensitivity of HPLC detectors increases as the molecular weights of the compounds increase

A

B

36
Q

Which of the following statements about columns containing more theoretical plates is TRUE?
A. Columns containing more theoretical plates make separations impossible.
B. Columns containing more theoretical plates interact irreversibly with the analyte.
C. Columns containing more theoretical plates take a long time to perform separations.
D. Columns containing more theoretical plates are better suited to separate a complex mixture.

A

D

37
Q

Which of the following is NOT an application of high performance liquid chromatography?
A. Separation of pharmaceutical drugs
B. Analysis of proteins, drugs and explosives
C. Separation of lipids, fatty acids and steroids
D. Elimination of undesirable substances from blood

A

D

38
Q

It is the more common form of HPLC where the stationary phase is nopolar and the mobile phase is polar.
A. affinity
B. exclusion
C. normal-phase
D. reversed-phase

A

D

39
Q

Ion exchange particles carry fixed positive or negative charges. A sulfonic acid type resin has SO3-H+ groups were H+ can be exchanged for
A. cations
B. anions
C. small cations and large anions
D. small anions and large cations

A

A

40
Q

The correct order in which light passes through a UV-Vis spectrophotometer?
A. detector, sample, source, monochromator
B. source, monochromator, sample, detector
C. source, sample, monochromator, detector
D. monochromator, source, sample, detector

A

B

41
Q

What is the purpose of a monochromator?
A. To remove stray light from the room.
B. To serve as a polychromatic light source.
C. To focus light from the sample onto the detector.
D. To allow only light of a certain wavelength to pass from the source to the sample

A

D

42
Q

Which of the following demonstrates proper drying of cuvette?
A. dry using a desiccator
B. place in an oven to dry overnight
C. blot on absorbing towel or tissue paper and allow to air dry
D. none of the above

A

C

43
Q

A solution of 4.48 ppm KMnO, (158.04 g/mol) exhibits 85.9% transmittance in a 1.00-cm cell at 520nm. Calculate the molar absorptivity of KMnO4 at this wavelength.
A. 1.47x10^3 L/mol•cm
B. 2.33x10^3 L/mol•cm
C. 4.29x10^-4 L/mol • cm
D. 2.24x10^-5 L/mol • cm

A

B

44
Q

Which of the following is NOT a limitation of Beer’s law?
A. Light must be of a narrow wavelength range and preferably monochromatic.
B. Presence of fluorescent species solution may interfere in the final absorbance of solution.
C. At high concentration, molecules may polymerize, affecting the absorption of solution.
D. Beer’s law does not form the quantitative basis for all types of absorption spectroscopy.

A

D

45
Q

Widely used continuous atomization method in AAS. It is also the most reproducible of all liquid-sample introduction methods that have been developed for AAS to date.
A. Flame
B. Electrothermal
C. Direct-current plasma
D. Inductively coupled plasma

A

A

46
Q

A hollow cathode tube lamp is necessary in AAS because
A. The width of an atom’s absorption band is narrow.
B. Cathode lamps are cheaper to operate and maintain.
C. Continuous spectrum lamps do not emit at the proper intensity.
D. Continuous spectrum lamps cause ionization of the molecules.

A

A

47
Q

Which species is used to bombard the sample in mass spectroscopy?
A. alpha
B. neutrons
C. electrons
D. protons

A

C

48
Q

A mass spectrum plats the intensity of each ion versus its
A. m/z ratio
B. absorbance
C. wavenumber
D. chemical shift

A

A

49
Q

The peaks of the following bonds can be found at 23000 cm-1 in an IR spectrum EXCEPT
A. O-H bond
B. N-H bond
C. C-H bond
D. C-C bond

A

D

50
Q

Which of the following techniques can be used to heat a reaction to 200°C?
A. Use a Bunsen burner to heat the reaction vessel.
B. Use a heating mantle with stirring.
C. Place the reaction vessel in a sand bath with stirring.
D. Place the reaction vessel in a water bath with stirring.

A

C

51
Q

Which of the following can promote even boiling?
A. stones
B. chips
C. stir bars
D. all of the above

A

D

52
Q

Where should a thermometer be placed to determine the boiling point of the distillate?
A. inside the distilling flask and it should be just below the side arm of the flask
В. inside the distilling flask and it should be immersed in the mixture being distilled
C. inside the receiver
D. inside the adapter

A

A

53
Q

An organic compound decomposes at its boiling point. What is the most appropriate method for the recovery of the solid organic compound?
varez
A. steam distillation (sensitive)
B. vacuum distillation
C. fractional distillation
D. liquid-liquid extraction

A

A

54
Q

It allows for many successive distillations to take place at once. It contains indentations or a packing material with lots of surface area.
A. adapter
B. condenser
C. round bottom flask
D. fractionating column

A

D

55
Q

The boiling point of a liquid is the temperature at which the vapor pressure is
A. lesser than internal pressure
B. equal to internal pressure
C. equal to external pressure
D. greater than internal pressure

A

C

56
Q

When the solid and liquid phases are in equilibrium, the temperature of the system
A. decreases gradually
B. none of the given answers
C. increases gradually
D. remains constant

A

D

57
Q

A liquid mixture that has a constant boiling point and whose vapor has the same composition as the liquid.
A. azeotrope
B. ideal
C. non-ideal solution
D. eutectic mixture

A

A

58
Q

What is the main purpose of heating under reflux?
A. To provide a very high temperature so that slow reactions occur at faster rates.
B. To increase the rate of evaporation of the solvent to increase the product yield.
C. To heat the reaction mixture in a solvent at a constant temperature without the loss of any reagents.
D. None of the above.

A

C

59
Q

A reaction mixture needs to be cooled to -77°C after refluxing. Which of the following is the best method to be used?
A. Place the reaction vessel in an ice bath.
B. Place the reaction vessel in the freezer.
C. Place the reaction vessel in a salt and crushed ice mixture.
D. Place tie reaction mixture in a dry ice-acetone mixture.

A

D

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